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1. Field of the Invention
The present invention relates to the field of groundwater remediation systems, and more particularly, to a method and apparatus for treatment of contaminated groundwater.
2. Description of Related Art
As can be seen by reference to the following U.S. Pat. Nos. 5,341,877, 5,622,450, 5,623,992, 5,688,076, 5,846,434, 5,860,767, 5,879,108, 5,906,241, 6,048,134, 6,099,206, 6,158,924, 6,254,310 and 6,332,972, the prior art is replete with myriad and diverse treatment systems for contaminated soils and groundwater.
Methods are known for the treatment of groundwater that has been contaminated with volatile and semi-volatile compounds such as chemicals associated with fuels, solvents, coal tar wastes, and other hazardous materials that have been released and have leached into the subsurface of the earth. Compounds such as benzene, toluene, ethylbenzene, xylenes, methyl tertiary butyl ether, poly-nuclear aromatics (PAHs), vinyl chloride, dichloroethene (DCE), trichloroethene (TCE), tetrachloroethene (PCE), carbon tetra-chloride, and other groundwater contaminants can be remediated through aerobic and/or anaerobic degradation, or through oxidation with ozone gas. Current technologies use compressed or forced gas injection to remove contaminants physically by volatilization, chemically by oxidation, or biologically by enhancing the natural attenuation process for these contaminants. These current technologies include air or gas sparging, oxygen release compounds, and chemical injection. Additional control measures to address hydraulic mounding, lateral migration of the contaminants, and volatilization of the contaminants are among the requirements and drawbacks inherent in the current technologies used.
While all of the aforementioned prior art systems have some beneficial features, they are uniformly deficient with respect to their failure to provide a simple, efficient, and practical method and apparatus for treating contaminated groundwater that minimizes detrimental side effects.
As a consequence of the foregoing situation, there has existed a longstanding need for a new and improved method and apparatus for treatment of contaminated groundwater and the provision of such a system is stated objective of the present invention.
Briefly stated, the present invention provides a process where gas bubbles are produced under a partial vacuum and are dynamically agitated creating a vortex that allows for homogenization of the gas desired for dissolution into the affected aquifer. The technology is applied through installation of the apparatus into treatment wells. The treatment wells are installed as stand-alone wells where hydrogeological conditions are conductive; i.e., sandy aquifers, fractured bedrock aquifers, and/or in treatment cells where hydrogeological conditions are less conductive; i.e., saturated sediments that are clay rich. The system does not use a compressed gas, compressed air source, or forced air/gas through the use of compressors or blowers. Rather, it uses cavitation to produce a slight vacuum to draw gas or air through a snorkel apparatus that is attached to the gas mixing chamber of the unit. The unit is installed so that it is submerged in the treatment well, below the water table. The gas is expelled under a slight vacuum from the base of the unit through a perforated base plate. A turbine is turned at a high rate of rotations per minute below the perforated plate, and causes the cavitation and vortex dynamics. This produces very small gas bubbles resulting in large gas surface exposure to the groundwater being treated. The gas bubbles experience a long retention time due to their small size and from the vortex produced by the system, which keeps the bubbles in suspension. The vortex dynamics provides a constant and consistent flux of dissolved gas to the aquifer. This translates to an efficient, energy saving system that conserves the amount of gas needed to produce the dissolved gas levels desired.